A little knowledge on how things work in a foreign country would have helped. The world is never fair. People don't have the same rights everywhere in the world.
Modifying one's behaviour/actions accordingly is not a bad idea. I believe that all the British, Americans and Europeans living/working in the middle east countries don't do things in the same way as they do in their countries. They adapt and even learn to ignore stuff that is not in their hands.
Spot on. As above, I lived there for 5 years and I modified certain behaviours, little things -- I wouldn't have sworn at an Emirati, I wouldn't have stuck two fingers up at a driver that cut me off, I wouldn't have been overtly touchy with a female in a public place, I wouldn't be belligerently drunk in public, and I definitely wouldn't have worn a Qatar football shirt in public. All of those examples are really pretty trivial, but some behaviour that is trivial in the UK can have major consequences in the UAE (or Qatar for that matter).
I'm not saying that it's necessarily right that behaviours should have to be adapted (it's ridiculous that the British guy was arrested). But anyone thinking of going to Qatar for the World Cup should not expect that they can behave as they might do in the UK while they're over in Qatar with no consequences.